Photographic reproduction process



y 1958 H. B. COWDEN ETAL 2,835,575

' PHOTOGRAPHIC REPRODUCTION PROCESS Filed April 5. 1955 EXPOSURE 1oINTER/VAL LATENZ' IMAGE.

EMULSION Siagel l ALKAIUINE HYDRAZINE DEVELOPMENT I6 1516*1IARDENEDGELA77NS/LVER 1o S IageX/ W/l/l/A WHMDBVEDGELAW'SILVEIp lHYPO -$ULFITE DEVELOPMENT I6 l7 I6 HerberfIlCowden Alberf W Wise IN VENTORS Arromvsyg AGENT United States Patent PHQTGGRAPHIC REPRGDUCTIONPROCESS Herbert B. Cowden and Albert W. Wise, Rochester, N. Y.,assignors to Eastman Kodak Company, Rochester, N. 51., a corporation ofNew Jersey Application April 5, 1955, Serial No. 499,328

' 8 Claims. (Cl. 96-28) This invention relates to photography and moreparticularly, to a photographic copy method especially adapted to ofiicecopy work.

The Yackel and Yutzy U. S. Patent 2,596,756, granted May 13, 1952, andthe Yutzy and Yackel patent application Serial No. 267,447, filedJanuary 21, 1952, now U. S. Patent 2,716,059, granted August 23, 1955,describe photographic copying methods particularly adapted to ofiicecopy work wherein an unhardened gelatinosilver halide emulsion layer,preferably containing a gelatin tanning silver halide developing agent,is exposed to a two-tone subject (line or halftone subject) followed bytreatment with an alkaline solution to obtain a hardened gelatin andsilver image in the exposed portion of the emulsion layer. The emulsionlayer, while moist, is then pressed into contact with an absorbentreceiving sheet to cause only the unhardened portion of the emulsionlayer to adhere to the receiving sheet with the result that when thesheet is removed from the emulsion layer, a thin stratum of theunhardened portions of the emulsion is found to be adhered to the sheet.

The mentioned processes are particularly adapted to the reproduction ofpositive originals such as printed subject matter which contain smalldark images on a comparatively large light-colored background. In thecase where it is desired to reproduce negative subject matter, such aspaper or film negative which have a light-colored image on acomparatively large dark background, the mentioned processes are lessuseful since in the final transfer step, it is necessary to transferlarge areas of the unexposed portions of the emulsion layer to thereceiving sheet with the result that the copies, when first made, tendto curl and may be somewhat sticky. Also, the large areas which aretransferred are fragile and easily damaged during the mechanical stepsof the process with the concomitant loss of definition in the copy.Also, such large areas may transfer as rather thick strata, leaving onthe printing element insufiicient nnhardened portions of emulsion forthe preparation of additional copies.

We have discovered that if a certain type of direct positive emulsion isused in the processes mentioned, the procedures can be adapted to thereproduction of both negative and positive subject matter as eithernegative or positive copy and the mentioned disadvantages overcome.

One object of our invention is to provide the direct positive elementuseful in the processes of our invention. Other objects reside inproviding the procedures for use of the direct positive emulsions in thementioned colloid image transfer processes.

The processes of our invention include exposing an unhardened directpositive emulsion of the nature indicated hereinafter to a line orhalftone subject, followed by developing either the exposed or unexposedportions with an alkaline solution in the presence of a gelatin tanningsilver halide developing agent which may or may ice not be present inthe original emulsion layer, under conditions of gelatin tanning silverhalide development, so as to obtain a hardened gelatin and silver imagein the emulsion layer. Thereafter, the emulsion is developed withanother alkaline solution in the presence of a silver halide developingagent and a compound inhibiting gelatin tanning so as to develop anunhardened gelatin and silver image in the remaining region of theemulsion layer. In addition, either one of the alkaline solutionscontains a silver halide solvent such as sodium thiosulfate when theother alkaline solution contains a hydrazine compound except that thefirst alkaline solu tion should not contain an amount of sulfitesufi'icient to inhibit gelatin tanning silver halide development. Thus,in a negative-positive process the first alkaline solution may containthe hydrazine compound but is substantially free of sulfite or othercompound inhibiting gelatin tanning and the other alkaline solutioncontains a silver halide solvent and a gelatin tanning inhibitor.Conversely, in a positive process the first alkaline solution containsthe silver halide solvent except no substantial amount of sulfite, andthe second alkaline solution contains the hydrazine compound and gelatintanning inhibitor. Following this, the emulsion layer is squeegeed orpressed against a receiving sheet to transfer a thin stratum of theunhardened gelatin and silver image to the receiving sheet. Theparticular alkaline solutions in which the hydrazine compound and thesilver halide solvent are incorporated determine whether a negative orpositive reproduction is obtained. In the specific Example Ill providedhereinafter, a negativepositive process is illustrated since thehydrazine compound is present in the first alkaline developer solutionand the silver halide solvent is present in the second non-tanningalkaline developer solution, the first alkaline solution causing tanningdevelopment in the unexposed portions of the direct positive emulsionlayer and the other alkaline solution causing non-tanning development inthe exposed portions of the emulsion layer.

The direct positive types of emulsion used in our in vention are thoseknown as internal latent image emulsionsthat is, emulsions which formlatent images mostly inside the silver halide grains. To the internallatent image emulsions may be added one or more gelatin tanning silverhalide developing agents. An internal latent image emulsion, that is,one which forms the latent image mostly inside the silver halide grains,as described on pages 296 and 297 of Mees The Theory of the PhotographicProcess, 1942, is especially useful for the process of my invention.Most of the internal latent image emulsions to which the gelatin tanningsilver halide developing agents may be added are silver bromoiodideemulsions of high iodide content, preferably containing at least l0%-20%of iodide. Burtons emulsion is an emulsion of this type, having a silveriodide content of approximately 40% of the content of silver halide. Itis not absolutely essential, however, for the emulsion to contain silveriodide.

Burtons emulsion described in Walls Photographic Emulsions, 1929, pages52 and 53, is an emulsion of this type prepared as follows:

Dry gelatin grams 250 (B is heated to 70 C., and A, cold, added to Bwith constant shaking, digested for 20 minutes at 50 C., and allowed tocool slowly. C is added after being allowed to swell for 20 minutes inwater, drained and melted. The emulsion is then set and washed.)

A gelatin tanning silver halide developing agent can then be added tothe emulsion in the manner described in the examples hereinafter.

An internal latent image emulsion made as described in the Davey andKnott U. S. Patent 2,592,250 is particularly useful in the processes ofour invention. This emulsion is prepared by first forming in the absenceof ammonia and in one or more stages silver salt grains consisting atleast partly of a silver salt which is more soluble in water than silverbromide, subsequently converting the grains to silver bromide or silverbromoiodide and if the silver iodide content of the emulsion is lessthan 6% calculated on the total silver halide, preferably treating suchgrains with an iodine compound to bring the silver iodide up to at least6%, ripening preferably in the absence of ammonia and then eitherwashing out some of the soluble salts or washing out the whole of thesoluble salts, followed by the addition of soluble salts such as solublechloride or bromide. An example of an emulsion made in this way is asfollows:

Solution No. l:

Inert gelatin 20 grams KCl 20 grams at 40 C. Water 560 cc.

Solution No. 2:

KCl 100 grams 0 Water 520 cc. l 0

Solution No. 3:

AgNO 195 grams Water 520 cc. l 45 Solution No. 4:

KBr 160 grams KI 40 grams at 45 C. Water 500 cc.

Run solutions Nos. 2 and 3 simultaneously into solution No. 1 in avessel, taking 90 seconds to do this. Then ripen for 1 minute at 45 C.Next add solution No. 4,

then ripen for 20 minutes at 45 C. Next add 235 grams of inert gelatin(dry). Then ripen at 45 C. for minutes during which time the gelatindissolves. Set and shred the emulsion and then wash until free from allsoluble bromide and then add about 150 cc. of 10% solution of KCl (byweight), and then add water to make 3 /2 liters. The tanning developingagents such as described hereinafter may then be added to the meltedemulsion.

An internal latent image type of silver halide emulsion may be definedas one which, when a test portion is exposed to a light intensity scalefor a fixed time between M and 1 second, and developed for 4 minutes atF. in the ordinary, surface developer (Example I), exhibits a maximumdensity not greater than /3 the maximum density obtained when the sameemulsion is equally exposed and developed for 3 minutes at 20 C. in aninternal type developer (Example II). Preferably the maximum densityobtained with the surface developer is not greater than the maximumdensity obtained when the same emulsion is developed in the internaltype developer. Stated conversely, an internal latent image emulsion,when developed in an internal type cleveloper (Example II) exhibits amaximum density at least 5, and preferably at least 10, times themaximum density obtained when the same emulsion is exposed 2,835,675 I iA 4 in the same way and developed in a surface developer (Example I).

An ordinary, surface-type developer, that is, one which develops animage only on the surface of the grains of an internal latent imageemulsion, is the following:

Example I Grams p-Hydroxyphenylglycine 10 Sodium carbonate (crystals)100 Water to 1 liter.

(Development time, 4 min. at 20 C.)

An internal type developer, that is, one which develops an image insidethe grains of an internal latent image emulsion, is the following:

Example II Grams Hydroquinone 15 Monemethyl-p-aminophenol. sulfate 15Sodium sulfite (anhydrous) 50 Potassium bromide 10 Sodium hydroxide 25Sodium thiosulfate (crystals) 20 Water to 1 liter.

(Development time, 3 min. at 20 C.)

The internal latent image emulsions useful in our invention, such asdescribed above, are separate and distinct from direct positiveemulsions, such as described in the Kendall U. S. Patent 2,541,472,which are fogged before image-forming exposure. Such emulsions have notbeen found to be useful in our processes.

Our invention will now be described with particular reference to theaccompanying drawing and the following specific example:

Example III An internal latent image emulsion prepared as described bythe method of the Davey and Knott patent above and containing one mol ofsilver halide, 476 grams of gelatin and 4000 cc. of water, was melted at40 C. and the following additions made: 100 grams of 8% aqueous saponinsolution and 600 grams of a developer dispersion prepared by dissolving44.5 grams of 4-phenyl catcchol (3,4-dihydroxydiphenyl) in 67.5 grams ofdibutyl phthalate at C. and pouring slowly into a rapidly stirredsolution of 44.5 grams of gelatin and 44.5 cc. of 8% aqueous saponinsolution in 475 cc. of water at 50 C. The mixture wasthen coated over400 square feet of paper which had been made without addition of agelatin hardening agent. The accompanying drawing illustrates in greatlyenlarged crosssectional view the manner of use of the resulting elementhaving an unhardened internal latent image gelatino-silver halideemulsion 10 containing the gelatin tanning silver halide developingagent 4-phenyl catcchol on support 11. As shown, the emulsion layer 10is exposed to a subject 12 which may be either a negative or positiveline or halftone subject having the image 13 on the dark background 14until area 15 of the emulsion layer has been adequately exposed.

The exposed emulsion is then treated in the manner described in the IvesU. S. Patents 2,563,785 and 2,588,982 for 20 seconds with an alkalinesolution preferably containing an aromatic hydrazine (if the hydrazinehas not already been incorporated into the emulsion layer) such as thefollowing:

Grams Nazsog 2 p(,8-Methylsulfonamidoethyl) phenyl hydrazine 2 Na CO -HO NaOH 1.4

Water to 1 liter.

This treatment brings about tanning development of the emulsion layer 10only in the unexposed areas 16, a hardened gelatin and sliver imagebeing obtained therein, whereas development does not take place in theexposed areas 15 of the emulsion layer as shown in stage 2 of thedrawing.

Thereafter, the developed emulsion layer is directly treated with analkaline solution containing a silver halide solvent such as sodiumthiosulfate which dissolves the surface of the exposed silver halidegrains and uncovers the underlying internal latent image. The alkalinesolution also contains a compound such as sodium sulfite which inhibitstanning of the gelatin in the presence of the fogged silver halide andthe gelatin tanning silver halide developing agent, such as thefollowing solution:

Grams Na SO NHZCOQ'HZO Sodium thiosulfate Water, 1 liter.

If desired, urea or another gelatin softening agent may be added to theabove solution to facilitate the subsequent transfer operation. As aresult of this treatment, the internal latent image in the exposedsilver halide in area of the emulsion layer is uncovered and developedto silver; thus an unhardened gelatin and silver image is obtained inthat area 117 as shown in stage 3 of the drawings.

In order to now obtain a print from the resulting element containing theunhardened gelatin and silver image, the emulsion layer is squeegeed tofree it of excess moisture and while it is still moist the emulsionlayer is pressed into contact with a fairly dry absorbent surface orreceiving sheet such as paper, to cause only the unhardened emulsionareas to adhere to the paper. Thereafter the receiving paper is peeledoff of the emulsion layer to obtain a thin stratum 13 of the unhardenedgelatin and silver image 17 on the paper 19, as shown in stage 4 of thedrawing. Image 18 is therefore a negative with respect to the originalsubject 12.

In a similar manner, other copies can be obtained by merely rewettingthe emulsion of the element used for making the first print with thesolution containing sodium thiosulfate, squeegeeing the elementmomentarily and pressing it against a blank sheet of paper and peelingoff the print from the emulsion layer.

While in the described process it is preferred that the gelatin tanningsilver halide developing agent be incorporated into the emulsion layer,the more soluble tanning developing agents, such as hydroquinone andpyrogallol can be incorporated into the first-mentioned alkalinedeveloper solution, in which case it may be necessary also toincorporate a quantity of the same developing agent or even anon-tanning silver halide developing agent, such as p-methyl-aminophenolsulfate, in the second developer solution to insure that a printcontaining adequate density is obtained in the subsequent transfer step.It may also be necessary to incorporate additional developing agent intothe second alkaline processing solution in case the more soluble tanningdeveloping agents have been present originally only in the emulsionlayer and are found to unduly diffuse out in the first developing stepso that an insufficient amount of developing agent is present for thesecond developing step.

In a less preferred variation of the process just described in referenceto the drawing, it is possible to shorten the process materially asfollows: After exposure of the emulsion containing the tanningdeveloping agent as shown in stage 1 of the drawing, followed directlyby treatment with the alkaline hydrazine solution, the resuling emulsionlayer containing unhardened emulsion only in the exposed region, whilemoist, may be pressed into contact with a fairly dry receiving sheet inthe presence of a compound such as a sulfur compound which reacts withthe silver halide to form a dark image. For this purpose thiourea is asuitable compound which can be present on the surface of the receivingsheet. After pressing the emulsion and receiving sheet together they arestripped apart leaving a stratum of dark colored gelatin image on thereceiving sheet which is a negative with respect to the originalsubject. In place of thiourea may be used other compounds which reactwith the gelatinosilver halide image transferred to the receiving sheetto form an image of appreciable optical density, or cause the silverhalide to become developable, e. g., sodium sulfide, sodium stannite,stannous chloride, mercaptans or zinc sulfide.

The gelatin tanning silver halide developing agents which can be used inthe invention in the manner described include, for example,hydroquinone, catechol, and pyrogallol, although these gelatin tanningsilver halide developing agents are less preferred because of theirwater-solubility and wandering characteristics in gelatin emulsionlayers as mentioned. The most preferred gelatin tanning silver halidedeveloping agents are those which are substantially insoluble in water,for example,

3,4-dihydroxy diphenyl 2,5-dihydroxy diphenyl 2,3-dihydroxy diphenyl4-phenoxy catechol 4-(2-cyclopentenyl) catecholl,2-diethoxallyl-4-phenyl catechol 1,2,3-triethoxallyl pyrogallol3,4-dihydroxydiphenyl is especially useful as well as 4-phenoxy catecholbecause these compounds have high gelatin tanning silver halidedevelopment activity and are non-wandering in emulsion layers. The abovetwo ethoxallyl derivatives of catechol and pyrogallol are unique sincethey are very stable in the emulsion layers under adverse conditions oftemperature and humidity, yet these compounds readily hydrolyze in thealkaline processing solutions of the invention to yield thecorresponding tanning developing agents 4-phenyl catechol andpyrogallol.

The preparation of the three latter compounds tabulated above isdescribed in the Salminen et al. U. S. Patent 2,751,295, granted June19, 1956.

The hydrazine compounds which can be used in the alkaline solutionsemployed in the process of the invention as described above, have thegeneral formula in which at least two Rs are hydrogen atoms and whenless than four Rs are hydrogen atoms, the remaining Rs are aryl,aralkyl, acyl, or carboxylic acid amide groups. Preferably, thehydrazine compound does not contain more than one aralkyl, acyl, orcarboxylic acid amide group, although it may contain either one or twoaryl groups. The hydrazine compound may be present either in thedeveloping solution itself or in the emulsion. In the latter case, ofcourse, the development of the exposed emulsion layer (stage 1 of thedrawing) can be carried out with a simple alkaline solution containinglittle or no sulfite which would inhibit tanning development.

.Representative hydrazine compounds having the above formula and Whosestructures may be better understood from consideration of Ives U. S.Patent 2,588,982, granted March 11, 1952, are as follows: Hydrazinedihydrochloride Phenylhydrazine hydrochloride p-Bromphenylhydrazinehydrochloride p-Chlorphenylhydrazine hydrochloride 2,5-dichlorophenylhydrazine p-Tolyl hydrazine hydrochloride p-Toluene sulfonyl hydrazinea-Naphthylhydrazine p-Acetylphenylhydrazine a-Benzyl-a-phenylhydrazinehydrochloride n-Amyl succinyl dihydrazide Sodium sulfosuccinyldihydrazide Hydrazine dicarbonic dihydrazide Hydrazobenzenep-Hydrazinobenzoic acid p-Hydrazinobenzene sulfonic acid (sodium salt)Phenylhydrazine-m-sulfonic acid (sodium salt) Triphenyl phosphoniumchloride acetohydrazide fl-Phenyl acethydrazido pyridinium chlorideAddition product of phenyl hydrazine and l-phenyl-3-hydroxy-S-pyrazolonep,p-Dihydrazino-diphenyl-dihydrochloride 4-p-phenylene disemicarbazideThe hydrazines disclosed in U. S. Patents 2,663,732 and 2,618,565 arepreferred for use in the alkaline processing solutions of the inventionor in the emulsion layers. These hydrazines have the general formula inwhich D represents a divalent mononuclear arylene group of the benzeneseries, 11 represents a positive integer of from 1 to 5 and R representsan alkyl group of from 1 to 4 carbon atoms. Representative hydrazineshaving this general formula are as follows:

p-(Methylsulfonamidomethyl)-phenylhydrazine m- Methylsulfonamidomethyl-phenylhydrazine o- (M ethylsulfonamidomethyl -phenylhydrazinep-((i-Methylsulfonamidoethyl)-phenylhydrazinem-tp-ldethylsulfonamidoethyl)-phenylhydrazineofi-Methylsulfonamidoethyl) -phenylhydrazinem-(Methylsulfonamido)-phenylhydrazine p- Methyls ulfonamido-phenylhydrazine m- Ethylsulfonamido) -phenylhydrazine p-Ethylsulfonamido) -phenylhydrazine o- Methylsulfonamido -phenylhydrazineThe silver halide solvents which can be used in the alkaline processingsolutions of the invention as described above to dissolve the surface ofthe silver halide grains of the emulsion layer and to uncover theinternal latent image, include those silver halide solvents well knownin the art such as alkali metal and ammonium thiosulfates and sulfites,ammonium salts, ammonium hydroxide, alkali metal thiocyanates, sodiumbisulfite, potassium metabisulfite, etc.

The compounds used in the alkaline processing solutions of the inventionto inhibit the tanning of the emulsion layer in the desired regioninclude those compounds well known in the art to inhibit gelatin tanningsilver halide development, for example, alkali metal sulfites, borax andalkali metal formaldehyde bisulfites.

It is necessary for the successful operation of the invention that theemulsion layer be not harder than would be the case with gelatincontaining 0.25 oz. of formaldehyde (40% diluted 1 to 3 with water) or0.7 gram of dry formaldehyde per pound, when freshly coated or 0.1 oz.of the solution per pound for a sample aged three to six months. Byunhardened or substantially unhardened as used here and in the appendedclaims, it is to be understood that this means the hardness of the orderobtained with gelatin treated with formaldehyde under the conditionsabove. The emulsion can, of course, contain no formaldehyde whatsoever.Emulsion layers appreciably harder will not transfer satisfactorily.Similarly, if, after the final development step of the processes it isfound that the layer is too hard and to accommodate variations inhardness and tanning sometimes encountered, we can use variations oftemperature or pressure when making the transfer print. To this end weordinarily apply pressure or temperature or both when rolling thedeveloped emulsion down onto the receiving support. With an emulsionwhich transfers slowly with heat or pressure applied, we can, withoutuse of increased heat or pressure during the transfer operation, makethe transfer by treatment of the developed emulsion with solutionshaving a softening effect upon the colloid vehicle. Thus,

there may be incorporated into the alkaline solution used in the finaldevelopment step a suitable quantity of a compound having a softeningeffect upon gelatin such as urea, sodium nitrate, glycerol, formamide orethylene chlorohydrin.

In the above example, as illustrated in the drawings, the emulsion wasexposed by contact printing. If desired, the exposure can be made bywell known projection or reflex exposure methods. In some instances, aswhen the original subject contains both heavy black charactors such astypewritten matter, and fine light gray lines such as pencil marks, itmay be desirable to insert a separate exposure step either before orjust after the image exposure step illustrated in stage 1 of thedrawing. This exposure may be made with a halftone screen having about120 or 133 lines per inch in contact with the emulsion layer before orafter the image exposure. Otherwise the emulsion is processed asdescribed in the above specific example with the result that the finalcopy obtained on the receiving sheet is composed of a series of dots andthe dark and light images of the original are reproduced with adequatelegibility. This procedure is particularly applicable to the directpositive processes of U. S. Patent 2,596,756 and that variation of ourinvention described hereinafter where the original subject is a positiveand is reproduced as a positive. It is thus possible to use minimumsubject exposure required to reproduce low-density pencil lines withoutcausing the wide high-density lines to become indistinct and blurred inthe final copy.

In the mentioned variation of our process in which the silver halidesolvent is present in the first developing solution and the hydrazinecompound in the second, the internal latent image emulsion, such asprovided in Example III above, containing a gelatin tanning silverhalide developing agent, after exposure is treated with an alkalinedeveloping solution such as a sodium carbonate solution containing asilver halide solvent, such as sodium thiosulfate, under conditions oftanning development, that is, the solution should be substantially freeof sulfite, to uncover the internal latent image in the exposed emulsionregion and develop a hardened gelatin and silver image only in theexposed area of the emulsion layer. Thereafter the emulsion is developedwith an alkaline solution such as provided in the above specific exampleand containing the hydrazine compound and sodium sulfite to obtain anunhardened gelatin and silver image in the unexposed portion of theemulsion layer. A direct-positive print is then obtained by merelypressing the emulsion layer against an absorbent receiving surface totransfer a thin stratum of the unhardened image area to the receivingsurface. In this process, the tanning developing agent may also bepresent only in the first alkaline developing solution rather than inthe emulsion layer and then it may be necessary to add silver halidedeveloping agent of either the tanning or nontanning variety to thesecond alkaline developing solution to insure adequate density in thefinal print.

We claim:

1. A photographic reproduction process which comprises exposing to atwo-tone subject an unhardened gelatino-silver halide emulsion layer atest portion of which upon exposure to a light intensity scale for afixed time between and 1 second and development for 3 minutes at 20 C.in the following internal type developer (II):

Water to 1 liter.

gives a maximum density at least 5 times the maximum density obtainedwhen the equally exposed silver halide emulsion is developed for 4minutes at 20 C. in the following surface developer (1):

Water to 1 liter.

developing said exposed emulsion layer with an alkaline solution in thepresence of a gelatin tanning silver halide developing agent underconditions of gelatin-tanning silver halide development until a hardenedgelatin and silver image is obtained in the emulsion layer, thereafterdeveloping said emulsion layer with an alkaline solution in the presenceof a silver halide developing agent and a compound inhibiting gelatintanning, until an unhardened gelatin and silver image is obtained in theremaining regions of the emulsion layer, pressing an absorbent sheetagainst said emulsion layer while the emulsion layer is moist to causethe unhardened gelatin and silver image to adhere to said sheet, andseparating said sheet and emulsion layer to transfer only a stratum ofsaid unhardened gelatin and silver image to said sheet, only one of saidalkaline solutions containing a silver halide solvent when the othercontains a hydrazine compound having the general formula in which atleast 2 Rs are hydrogen atoms and when less than 4 Rs are hydrogenatoms, the remaining Rs are selected from the class consisting of aryl,aralkyl, acyl and carboxylic acid amide groups, but not more than one Ris any one of said aralkyl, acyl and carboxylic acid amide groups.

2. A photographic reproduction process which comprises exposing to atwo-tone subject an unhardened gelatino-silver halide emulsion layer atest portion of which upon exposure to a light intensity scale for afixed time between ,5 and 1 second and development for 3 minutes at 20C. in the following internal type developer Grams Hydroquinone l5Monomethyl-p-aminophenol sulfate l5 Anhydrous sodium sulfite 50Potassium bromide Sodium hydoxide 25 Sodium thiosulfate 20 Water to 1liter.

gives a maximum density at least 5 times the maximum density obtainedwhen the equally exposed silver halide emulsion is developed for 4minutes at 20 C. in the following surface developer (I):

Grams p-Hydroxyphenylglycine 10 Sodium carbonate 100 Water to 1 liter.

said emulsion containing a gelatin tanning silver halide developingagent, treating the exposed emulsion layer with an alkaline solutioncontaining a hydrazine compound having the general formula conditions ofgelatin tanning silver halide development until a hardened gelatin andsilver image is obtained only in the unexposed portion of the emulsionlayer, treating the resulting developed emulsion layer with an alkalinesolution containing a silver halide solvent and a compound inhibitinggelatin tanning, until an unhardened gelatin and silver image isobtained in the exposed portion of the emulsion layer, pressing anabsorbent sheet against said emulsion layer while the emulsion layer ismoist to cause the unhardened gelatin and silver image to adhere to saidsheet, and separating said sheet and emulsion layer to transfer only astratum of said unhardened gelatin and silver image to said sheet.

3. The process of claim 1 wherein said first mentioned alkalinedeveloping solution contains a silver halide solvent and said otheralkaline solution contains the designated hydrazine compound and acompound inhibiting gelatin tanning.

4. The process of claim 1 wherein the silver halide solvent is an alkalimetal thiosulfate and the compound inhibiting gelatin tanning is analkali metal sulfite.

5. A photographic reproduction process which comprises exposing to atwo-tone subject an unhardened gelatino-silver halide emulsion layer atest portion of which upon exposure to a light intensity scale for afixed time between A and 1 second and development for 3 minutes at 20 C.in the following internal type developer (II):

- Grams Hydroquinone 15 Monomethyl-p-aminophenol sulfate 15 Anhydroussodium sulfite 50 Potassium bromide 10 Sodium hydroxide 25 Sodiumthiosulfate 20 Water to 1 liter.

gives a maximum density at least 5 times the maximum density obtainedwhen the equally exposed silver halide emulsion is developed for 4minutes at 20 C. in the following surface developer (1):

Grams p-Hydroxyphenylglycine 10 Sodium carbonate Water to 1 liter.

said emulsion layer containing a compound of the class consisting of3,4-dihydroxy diphenyl 2,5-dihydroxy diphenyl 2,3-dihydroxy diphenyl4-phenoxy catechol 4-(2-cyclopenteny1) catechol1,2-diethoxallyl-4-phenyl catechol 1,2,3-triethoxallyl pyrogalloldeveloping the exposed emulsion layer with an alkaline solutioncontaining a compound of the class consisting of until a hardenedgelatin and silver image is obtained only in the unexposed portion ofthe emulsion layer, treating the resulting developed emulsion layer withan alkaline solution containing an alkali metal sulfite and an alkalimetal thiosulfate until an unhardened gelatin and silver image isobtained in the exposed portion of the emul- 11 sion layer, pressing anabsorbent sheet against said emulsion layer while the emulsion layer ismoist to cause the unhardened gelatin and silver image to adhere to saidsheet, and separating said sheet and emulsion layer to transfer only astratum of said unhardened gelatin and silver image to said sheet.

6. A photographic reproduction process which comprises exposing to atwo-tone subject an unhardened gelatino-silver halide emulsion layer atest portion of which upon exposure to a light intensity scale for afixed time between and 1 second and development for 3 minutes at 20 C.in the following internal type developer (II) Water to 1 liter.

gives a miximum density at least 5 times the maximum density obtainedwhen the equally exposed silver halide emulsion is developed for 4minutes at 20 C. in the following surface developer (I) Gramsp-Hydroxyphenylglycine 10 Sodium carbonate 100 Water to 1 liter.

said emulsion layer containing 3,4-dihydroxy diphenyl as a gelatintanning silver halide developing agent, developing the exposed emulsionlayer with an alkaline solution containingp-(p-methylsulfonamidoethyl)phenyl hydrazine,

until a hardened gelatin and silver image is obtained only in theunexposed portion of the emulsion layer, treating the-resultingdeveloped emulsion layer with an alkaline solution containing sodiumthiosnlfate and sodium sulfite so as to obtain an unhardened gelatin andsilver image in the exposed portion of the emulsion layer, pressing anabsorbent sheet against said emulsion layer while the emulsion layer ismoist to cause the unhardened gelatin and silver image to adhere to saidsheet, and separating said sheet and emulsion layer to transfer only astratum of said unhardened gelatin and silver image to said sheet.

7. The process of claim 1 wherein the hydrazine compound used has thegeneral formula wherein D represents a divalent mononuclear arylenegroup of the benzene series, n represents a positive integer of from 1to 5, and R represents an alkyl group of from 1 to 4 carbon atoms.

8. The process of claim 2 wherein the hydrazine compound used has thegeneral formula wherein D represents a divalent mononuclear aryl groupReferences Cited in the file of this patent UNITED STATES PATENTS Yutzyet al. May 13, 1952 Yutzy et al. Aug. 23, 1955

1. A PHOTOGRAPHIC REPRODUCTION PROCESS WHICH COMPRISES EXPOSING TO ATWO-TONE SUBJECT AN UNHARDENED GELATINO-SILVER HALIDE EMULSION LAYER ATEST PORTION OF EWHICH UPON EXPOSURE RO A LIGHT INTENSITY SCALE FOR AFIXED TIME BETWEEN 1/11 AND 1 SECOND AND DEVELOPMENT FOR 3 MINUTES AT20*C. IN THE FOLLOWING INTERNAL TYPE DEVELOPER (11):